The largest subunit of eukaryotic RNA polymerase II contains a carboxyl-terminal domain (CTD) which is comprised of repetitive hepatapeptides with a consensus sequence Tyr1-Ser2-Pro3-Thr4-Ser5-Pro6-Ser7. We demonstrate here that the mouse CTD expressed in and purified from Escherichia coli can be phosphorylated in vitro by a p34(cdc2/CDC28)-containing CTD kinase from mouse ascites tumor cells. The product of this reaction, a phosphorylated form of the CTD, contains phosphoserine and phosphothreonine, but not phosphotyrosine. The same phosphoamino acid content is observed in the in vivo phosphorylated CTD from a mouse cell line. Synthetic peptides with naturally occurring non-consensus heptapeptide sequences can also be phosphorylated by CTD kinase in vitro. Phosphoamino acid analysis of these non-consensus heptapeptides together with direct sequencing of a phosphorylated heptapeptide reveals that serines (or threonines) at positions two and five are the sites phosphorylated by mouse CTD kinase. Thus, the -Ser(Thr)-Pro- motif common to p34(cdc2/CDC28)-containing protein kinases is the recognition site for mouse CTD kinase.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - 1991|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology